1. Field of the Invention
Example embodiments of the present invention in general relate to a light emitting diode (LED) lighting fixture.
2. Description of the Related Art
LEDs are widely used in consumer lighting applications. In consumer applications, one or more LED dies (or chips) are mounted within a LED package or on an LED module, which may make up part of a LED lighting fixture which includes one or more power supplies to power the LEDs. Various implementations of the LED lighting fixtures are available in the marketplace to fill a wide range of applications, such as area lighting (roadway and/or parking lot illumination) indoor lighting, backlighting for consumer electronics, etc.
Conventional area lighting such as roadway lights uses high pressure sodium (HPS) bulbs which provide omni-directional light. Reflectors are used to direct some of this light, but much of the light is lost illuminating unintended spaces. For example with HPS bulbs, the typical lumen amount will be in the tens of thousands of lumens, but all of that output does not illuminate the intended area, such as a roadway area for example.
LEDs offer improved light efficiency, a longer lifetime, lower energy consumption and reduced maintenance costs, as compared to HPS light sources. Conventional HPS bulbs are susceptible to maintenance loss and surface, dirt and other losses. Conventionally, area lighting fixtures used for roadway illumination are attached on poles and include omni-directional HPS bulbs with reflectors to illuminate the roadway in different patterns based on different situations.
FIGS. 1A to 1G show types of roadway illumination. As shown in FIGS. 1A to 1G, there are five primary types of roadway illumination. The Illuminating Engineering Society of North America (IESNA) is the recognized technical authority on illumination and puts out specifications for the five primary types of roadway illumination.
Type I illumination is a direct illumination in two directions along the direction of the roadway (if the road is a single road) and/or in a straight directional pattern at a cross section as shown in FIG. 1B. FIG. 1C illustrates a Type II pattern and shows a lighting fixture which directs light at an angle to normal in either two directions, or in four directions as shown in FIG. 1D.
Type III illumination in FIG. 1E shows a different angled illumination from normal as compared to Type II in FIG. 1C, where the angle of illumination from normal is narrower to reflect a smaller coverage area. Type IV illumination (FIG. 1F) has an even narrower angle of illumination from normal to create a different, smaller illumination area than either Type II or Type III. The omni-directional lighting pattern across the entire intersection which characterizes Type V illumination is shown in FIG. 1G.
Conventional HPS lighting fixtures must be replaced with a completely different fixture to change the lighting pattern at a given location. In order to change the shape and brightness of light output from a given HPS fixture, there is no way to adjust the pattern other than replacing the entire fixture. Similarly for LED lighting fixtures mounted on poles for area lighting applications, to change the shape and brightness, the entire fixture typically must be replaced.